Based on the distinct patterns of signs and symptoms, three different clinical syndromes have been grouped together under the category of "frontotemporal dementia" (FTD):
- Behavioral-variant frontotemporal dementia (bvFTD)
- Semantic dementia (SD) and
- Progressive non-fluent aphasia (PNFA).
Previously, researchers sometimes used “FTD” to refer only to bvFTD, which has also been called "frontal variant FTD" (fvFTD) or Pick’s Disease. The language variants (SD and PNFA) are sometimes grouped together under the term "primary progressive aphasia" (PPA). PPA has since been split into three subgroups: progressive non-fluent aphasia, semantic dementia and logopenic progressive aphasia (LPA). At autopsy, patients with LPA are often found to have Alzheimer’s disease, not FTLD. SD was previously referred to at times as "temporal variant FTD" (tvFTD).
A small number of people affected by FTD also develop motor neuron disease (FTD/MND), (sometimes called FTD with amyotrophic lateral sclerosis or FTD/ALS).
Corticobasal degeneration (CBD), also called corticobasal syndrome or corticobasal ganglionic degeneration, and progressive supranuclear palsy (PSP) are two related diseases that are not classified as FTD but often share some symptoms with FTD.